In general, electric motors operate by rotating a rotor relative to a fixed stator by varying the orientation of a magnetic field induced by one or more windings. In some electric motors, both the rotor and stator include windings. In such an induction motor, the magnetic field induced by the stator windings induces current within the rotor windings which, due to Lenz's law, causes a resultant torque on the rotor, thus causing rotation.
In a permanent magnet motor, on the other hand, the rotor includes one or more permanent magnets. The permanent magnets, in attempting to align with the magnetic field induced by the windings in the stator, cause a resultant torque on the rotor. By varying the orientation of the magnetic field, the rotor may thus be caused to rotate. In high-torque permanent magnet motors, multiple permanent magnets may be positioned on the exterior of the rotor (for an internal rotor permanent magnet motor).
While in operation, the components of the electric motor may heat up in response to, for example, electrical resistance in the stator windings, mechanical friction, etc.